Examination of the modified monostandard method in neutron activation analysis

The reproducibility, the small scale as well as the large scale variability of¹³⁷Cs extracted sequentially from the soil by using a modified Tessier procedure was investigated at several grassland sites in Bavaria/Germany and in the Chemobyl area. Because undisturbed grassland soils are never homogeneous with respect to their soil properties, all sequential extractions at the German sites were carried out at each plot separately for different soil layers (e.g., 0–2, 2–5, 5–10, 10–15, 15–20 and 20–30 cm). The results show that the coefficients of variation (CV) for the reproducibility of the extraction procedure for¹³⁷Cs was (with some exceptions) around 10–20% for all fractions. For the small scale variability of¹³⁷Cs (samples within an area of 10×10m²) the values for theCV were (again with a few exceptions) in the same range. Compared to that, the large scale variability of extractable¹³⁷Cs (random soil samples within an area of 100×200 km²) was higher for all fractions, even though only moderately. The implications of these results with respect to a sampling design are discussed.     

Electrocatalysis of cytochrome c at a C(60)-gamma-cyclodextrin and Nafion chemically modified electrode

The C(60)-gamma-cyclodextrin and Nafion chemically modified electrode exhibits two redox waves by cyclic voltammetry. Such an electrode will effect reduction and oxidation of cytochrome c and be capable of mediating the electron transfer to cytochrome c.     

吡啶叶立德与查尔酮1,3-偶极环加成反应制备2-苯基-3-乙酰基中氮茚

报道在氧化剂存在下吡啶叶立德与查尔酮进行1,3-偶极环加成反应, 一锅法合成2-苯基-3-乙酰基中氮茚化合物的方法, 收率37%. 用类似的方法由α-溴代异喹啉季铵盐、查尔酮、碱和氧化剂进行反应, 可一锅法得到1-苯甲酰基-2-苯基-3-乙酰基吡咯并[2,1-a]异喹啉, 收率58%.     

水热法合成的MoVTeNbOx多组分氧化物催化剂上异丁烷的选择氧化

采用水热法合成了MoVTeNbOx多组分氧化物催化剂, 并用XRD, ICP, BET和SEM等方法对催化剂进行了表征, 考察了MoVTeNbOx多组分氧化物催化剂的组成、反应温度和空速对异丁烷选择氧化反应性能的影响. 其中组成为MoV0.3Te0.17Nb0.12Ox的催化剂显示出最好的催化活性和选择性, 在673 K下, 异丁烷的转化率为10.8%, 甲基丙烯醛(MAL)和甲基丙烯酸(MAA)的收率累积达到6.5%.     

不同取向的CoSb3纳米线阵列的电化学法制备

近年来,金属纳米线及其阵列由于其新奇的物理和化学特性和在纳米器件方面潜在的应用前景,越来越受到人们的关注。氧化铝模板合成一维纳米材料具有设备简单、制作方便等优点,因而成为近年来人们常用的一种方法。利用电化学沉积的方法在多孔氧化铝模板中沉积各种成分的纳米线已成为纳米材料制备的一种常见的方法。这种方法不仅可以得到大面积有序的纳米线阵列,还可以根据需要调节孔洞的大小来控制纳米线的直径[1￣3]。最近理论研究结果预言[4￣6],由于纳米材料的量子限域效应,热电材料的纳米线将有比其相应块体材料更高的品质因数n,这极大地激…     

KINETICS OF POLYMERIZATION OF ACRYLONITRILE INITIATED BY VANADIUM(V)-THIOUREA REDOX SYSTEM

The kinetics of polymerization of acrylonitrile (AN) initiated by quinquevalent vanadium (V~(5+))-thiourea (TU) redox system has been investigated in aqueous nitric acid in the temperature range from 30 to 50℃. The polymerization rate (R_p) can be expressed as follows: In the copolymerization of acryionitrile with methyl acrylate (MA), the reactivity ratios were found to be 1.0 and 1.1, respectively. The experimental observations suggest that the initiating species is probably a complex consisting of a central ion of Lewis acid-VO_2~+ and the ligands of Lewis bases-acrylonitrile, thiourea, and nitrate anions, while the initiating system in lower concentration, the polymerization of acrylonitrile does not occur if the thiourea is acidified prior to its reaction with quinquevalent vanadium. This indicates that the primary radicals (or the monomeric radicals in the present article) are produced by associated thiourea rather than isothlourea.     

Investigation of pyrolysis of chinese coals using thermal analysis/mass spectrometry

TA/MS (thermal analysis coupled with mass spectrometry) was applied to the pyrolysis of Chinese coals with different ranks. A total of 13 Chinese coals were investigated. The samples were deliberately chosen to represent the 13 types of Chinese coals according to the Chinese coal classification system. The experiments were carried out in an argon atmosphere with a flow rate of 150 ml min^-1. The samples were heated from 40 up to 1200°C with a constant heating rate of 10 k min^-1. The main evolved pyrolysis products were identified through the on-line recorded mass spectra. The thermal and evolution behavior was compared between the coals. The results showed a strong thermal and evaluation behavior dependence on the coal rank. Different aliphatic fragments and also some aromatic substances, which are of environmental concern (BTX, PAHs), were found to be released depending on the different types of coal. This revised version was published online in July 2006 with corrections to the Cover Date.     

Nickel(II) complexes of a thiosemicarbazone prepared from 2-Acetylpyridine

Summary The ligand 3-azabicyclo[3.2.2]nonane-3-thiocarboxylic acid 2-[1-(2-pyridinyl)ethylidene]hydrazide (HL), which is observed in an unusual tautomeric form in the solid state, and its selenium analogue (HLSe) have been used to prepare a series of nickel(II) complexes. Compounds of the general formula [NiLX] (X=Cl, Br, NCS, N₃, NO₂ or NCSe) as well as [Ni(LSe)Cl] have been found to be diamagnetic, planar complexes. A single crystal study of [NiL(NCS)] shows the deprotonated ligand bound in a tridentate mannervia its pyridyl nitrogen, imine nitrogen and the thione sulphur atom with the nitrogen atom of the thiocyanato-ligand occupying the fourth coordination position. The solids prepared from the nickel(II) salts having tetrafluoroborate, nitrate and iodide ions approximate to octahedral symmetry and have neutral HL ligands coordinated in a bidentate fashionvia the pyridine and imine nitrogens with the remaining coordination sites being occupied by the anions or water molecules. The [NiL₂] solid is also octahedral with the two deprotonated ligands bonding as tridentate groupsvia the same atoms as in the [NiLX] complexes.